1. Field of the Invention
This invention relates to a small-sized magnetic disk cartridge capable of being loaded in an exchangeable manner into a disk drive, which is located in a digital still camera, a digital video camera, a notebook size personal computer, or the like.
2. Description of the Related Art
Various types of recording media have heretofore been releasably loaded into card slots of electronic equipments, such as digital still cameras, digital video cameras, and notebook size personal computers, for recording and reproduction of information. As the recording media, various types of recording media, such as semiconductor memory types of recording media, hard disk types of recording media, optical disk types of recording media, and small-sized magnetic disk types of recording media, e.g. floppy disks, have been used in practice.
Of the above-enumerated recording media, the semiconductor memory types of recording media are most popular for easiness of processing and large recording capacities. However, the semiconductor memory types of recording media have the drawbacks in that the cost is comparatively high. Therefore, ordinarily, after imaging operations have been performed with the digital cameras utilizing the semiconductor memory types of recording media, image signals having been obtained from the imaging operations and stored on the semiconductor memory types of recording media are transferred from the semiconductor memory types of recording media into personal computers, and the like, and stored in the personal computers, and the like. Thereafter, the image signals having been stored on the semiconductor memory types of recording media are erased, and the semiconductor memory types of recording media having been erased are reused for storing image signals.
As the hard disk types of recording media, the recording media having a recording capacity of 340 MB and the recording media having a recording capacity of 1 GB are known. However, as in the cases of the semiconductor memory types of recording media, the hard disk types of recording media have the drawbacks in that the cost cannot be kept low. Therefore, ordinarily, after data have been stored on the hard disk types of recording media, the data are transferred from the hard disk types of recording media into different apparatuses and stored in the different apparatuses. Thereafter, the data having been stored on the hard disk types of recording media are erased, and the hard disk types of recording media having been erased are reused for storing data.
The optical disk types of recording media have comparatively large recording capacities for their small sizes. For example, the optical disk types of recording media having a size of 35 mm×41 mm×11 mm have a recording capacity of 256 MB. Also, recently, research has been conducted to develop an optical disk type of recording medium having a recording capacity of as large as 512 MB. However, the optical disk types of recording media have the drawbacks in that a long time is required to write information, and the recording speed is low.
As for the small-sized magnetic disk types of recording media, such as floppy disks, there have heretofore been known the magnetic disks, which have a small size of approximately 50 mm×55 mm×2 mm and are capable of being loaded in an exchangeable manner into disk drives having a size that allows the disk drives to be inserted into card slots of personal computers, and the like. However, the magnetic disks have the drawbacks in that the recording capacities are as small as 40 MG and are not sufficient for the recording of image signals obtained with cameras, and in that the sizes are not appropriate for the use in digital cameras.
Recently, digital cameras have rapidly become popular for easiness of information recording, enhanced image quality owing to development of imaging devices, possibility of erasing and transfer of image signals, large recording capacities, and the like, coupled with a social background in which personal computers have become popular. However, as described above, the costs of the recording media are high, and the recording capacities of the recording media are limited. Therefore, limitation is imposed upon the manner in which the recording media are used. For example, as described above, since the recording media are expensive, instead of a plurality of recording media being prepared for one camera, one recording medium is ordinarily used iterately by, for example, transferring the recorded image signals into a personal computer when the recording medium is full of the image signals, and thereafter erasing the recorded image signals. Accordingly, the problems occur in that the recording medium becomes short of free recording region while the user of the recording medium is traveling, and in that the recording medium on which the image signals have been recorded cannot be preserved or given to another person.
Therefore, such that the users are capable of preserving the recording media, on which the image signals acquired with the digital cameras have been recorded, or are capable of freely giving the recording media to other persons, there is a strong demand for small-sized recording media, which have large recording capacities and are capable of being furnished at a low cost. Also, as for the recording media for use in personal computers, such that the users are capable of transferring the recording media, on which the data of the personal computers have been recorded, to other persons, there is a strong demand for small-sized recording media, which have large recording capacities and are capable of being furnished at a low cost.
In order for the demands described above to be satisfied, it may be considered to utilize recording media, which comprise a card type of disk drive capable of being loaded into electronic equipments, such as personal computers and digital cameras, and a magnetic disk cartridge capable of being loaded into the disk drive, as the small-sized recording media, which have large recording capacities and are capable of being furnished at a low cost, such that the users are capable of preserving the recording media, on which the image signals acquired with the digital cameras or the data of the personal computers have been recorded, or are capable of freely giving the recording media to other persons. Specifically, as the magnetic disk cartridge described above, it may be considered to utilize a magnetic disk cartridge having a recording capacity of, for example, at least 200 MB, and comprising a housing, which is provided with an openable shutter, and a flexible magnetic disk, which is capable of recording magnetic information at a high recording density and which is accommodated for rotation within the housing. As a high-recording-density magnetic recording medium for constituting the magnetic disk, a magnetic recording medium, which is provided with a thin metal film with a vacuum evaporation process of a sputtering process, or a magnetic recording medium, which utilizes barium ferrite particles or ferromagnetic metal particles, may be employed. The high-recording-density magnetic recording medium, which utilizes barium ferrite particles, is proposed in, for example, Japanese Patent Application No. 2001-312864 filed by the applicant.
The high-recording-density magnetic recording medium, which utilizes barium ferrite particles, is a magnetic disk, which comprises a magnetic layer containing the barium ferrite particles and utilizes the materials capable of achieving a high recording density. By way of example, the high-recording-density magnetic recording medium may be a magnetic recording medium proposed in Japanese Patent Application No. 2001-205290. The magnetic recording medium proposed in Japanese Patent Application No. 2001-205290 is a magnetic recording medium, comprising:                a non-magnetic substrate, a non-magnetic layer containing non-magnetic particles and a binder, and a magnetic layer containing ferromagnetic particles, which are hexagonal crystal system ferrite particles, and a binder, the non-magnetic layer and the magnetic layer being overlaid in this order on at least either one of two surfaces of the non-magnetic substrate,        wherein the non-magnetic layer contains carbon black, which has an average particle diameter falling within the range of 10 nm to 30 nm, in a proportion ranging from 10 parts by mass per 100 parts by mass of the non-magnetic particles to 50 parts by mass per 100 parts by mass of the non-magnetic particles,        the thickness of the magnetic layer is at most 0.2 μm,        a standard deviation “b” of intensity with respect to a mean intensity “a” of elements due to the ferromagnetic particles, as analyzed with an electron beam micro-analysis, satisfies the condition 0.03≦b/a≦0.4,        a surface roughness Ra, expressed in terms of arithmetic mean deviation, of the magnetic layer is at most 5 nm, and        a 10-point mean roughness Rz of the magnetic layer is at most 40 nm.With respect to the magnetic disk utilizing the material described above, for example, the recording and reproduction of information are performed by use of a magnetic head, such as an MR head, capable of achieving a high recording density.        
With the proposed magnetic recording medium, a high-recording-density recording medium having a recording capacity of at least 200 MB, preferably at least 500 MB, is capable of being achieved. Therefore, with the proposed magnetic recording medium, for example, it becomes possible to record the image signals, which represent 500 still images, on one recording medium in cases where a recording capacity of approximately 1 MB is required per still image. Also, as for dynamic images, it becomes possible to record the imaged contents, which are taken for a period of approximately 30 minutes, on one recording medium. Accordingly, the image signals representing the dynamic images having been imaged with a digital camera, the image signals representing the dynamic images having been transmitted from a portable telephone, and the like, are capable of being recorded on the recording medium. As a result, serviceableness to the user who utilizes the imaged contents is capable of being enhanced. Also, in cases where the proposed magnetic recording medium is utilized in a personal computer, the magnetic recording medium is capable of being utilized conveniently as a low-cost, large-capacity data storage medium, and therefore the magnetic recording medium has a high serviceableness.
FIG. 14A is a schematic explanatory view showing a conventional magnetic disk cartridge, a disk drive, and an electronic equipment provided with a card slot, into which the disk drive is to be loaded. FIG. 14B is a schematic explanatory view showing a conventional magnetic disk cartridge, a disk drive, and a digital camera provided with a socket, into which the disk drive is to be loaded. In this specification, examples of the disk drives should preferably include a disk drive 6 for use in a personal computer, which disk drive is illustrated in FIG. 14A, a disk drive incorporated in a PC card, such as “click!” (trade name), and a disk drive 6′ for use in a digital camera 3, or the like. As illustrated in FIG. 14A, the disk drive 6 is loaded to and electrically connected to a socket 4 of a receiving section of a PC card 2, which is to be inserted into a PC card receiving slot of the personal computer. Also, as illustrated in FIG. 14B, the disk drive 6′ is loaded to and electrically connected to a socket of a receiving section 5 of the digital camera 3. Therefore, each of the disk drive 6 and the disk drive 6′ has a markedly small size. For example, each of the disk drive 6 and the disk drive 6′ has a length falling within the range of 38 mm to 55 mm, a width falling within the range of 35 mm to 51 mm, and a thickness falling within the range of 3 mm to 5 mm. Also, for example, each of a magnetic disk cartridge 8 shown in FIG. 14A and a magnetic disk cartridge 8′ shown in FIG. 14B has a length falling within the range of 25 mm to 36 mm, and a thickness falling within the range of 1 mm to 3 mm.
It has been proposed to form a housing of a small-sized magnetic disk cartridge into a circular disk-like shape and to process the magnetic recording medium with a feeling of a coin. Specifically, it has been proposed to process the magnetic recording media with a light-hearted feeling as in the cases where coins are put into an automatic vending machine, and thereby to enhance the serviceableness of the magnetic recording medium.
However, in cases where the housing of the magnetic disk cartridge is formed into the circular disk-like shape, it is necessary that an orientation of the magnetic disk cartridge, in which the magnetic disk cartridge is to be inserted into the disk drive, is capable of being discriminated. Specifically, in cases where the housing of the magnetic disk cartridge is formed into the circular disk-like shape, the problems occur in that the magnetic disk cartridge is capable of being inserted into the disk drive regardless of the orientation of the shutter, which is secured in an openable manner to the housing of the magnetic disk cartridge. If the shutter openable secured to the housing of the magnetic disk cartridge is located at a position other than a predetermined position within the disk drive, the recording of information on the magnetic disk accommodated within the housing of the magnetic disk cartridge and the reproduction of the information from the magnetic disk cannot be performed. Therefore, it is necessary that the housing of the magnetic disk cartridge be located in a predetermined orientation with respect to the disk drive.
Also, for example, in cases where the magnetic disk cartridge is loaded into the disk drive, a position adjusting hole or a position adjusting recess of the housing of the magnetic disk cartridge is fitted onto and engaged with a protrusion formed on the side of the disk drive, and the magnetic disk cartridge is thus set at the predetermined position within the disk drive. However, if the engagement between the position adjusting hole or the position adjusting recess of the housing of the magnetic disk cartridge and the protrusion formed on the side of the disk drive is loose even slightly, the relationship between the position of the magnetic head of the disk drive, which magnetic head is capable of achieving a high recording density, and the position of the magnetic disk on the side of the magnetic disk cartridge will fluctuate, and the recording and reproducing characteristics will be affected adversely.
Further, since the size of the magnetic disk cartridge is markedly small, the problems occur in that the releasability of the magnetic disk cartridge from the disk drive is low, and the magnetic disk cartridge cannot be easily taken out from the disk drive.
Furthermore, since the size of the magnetic disk cartridge is markedly small such that the magnetic disk cartridge is capable of being processed with a feeling of a coin, when the magnetic disk cartridge is picked up between the fingers, the entire areas of the front and back surfaces of the magnetic disk cartridge are covered with the fingers. Therefore, it becomes difficult to confirm visually which surface is the front surface or the back surface of the magnetic disk cartridge. Also, in cases where both the front and back surfaces of the magnetic disk cartridge having the circular disk-shaped housing are constituted of approximately flat surfaces, there is the risk that the magnetic disk cartridge will be inserted into the disk drive in an incorrect orientation with respect to the front and back surfaces of the magnetic disk cartridge.
As described above, if the magnetic disk cartridge is inserted incorrectly into the disk drive, the magnetic disk cartridge will not be located at the predetermined position within the disk drive, and therefore the recording of information on the magnetic disk accommodated within the housing of the magnetic disk cartridge and the reproduction of the information from the magnetic disk cannot be performed. Accordingly, in such cases, the orientation of the magnetic disk cartridge, in which the magnetic disk cartridge is inserted into the disk drive, must be corrected, and the magnetic disk cartridge must again be inserted in the correct orientation into the disk drive. As a result, the operating efficiency cannot be kept high. Also, if the magnetic disk cartridge is inserted forcibly into the disk drive in an incorrect orientation with respect to the front and back surfaces of the magnetic disk cartridge, there will be the risk that the magnetic disk cartridge will breakdown. Therefore, there is a strong demand that the front and back surfaces of the magnetic disk cartridge are capable of being discriminated accurately.
Also, as for ordinary living necessaries, in order to protect users and consumers of the living necessaries, there have heretofore been taken safety countermeasures, such as attaching of sheets, on which instructions have been written, to the products. However, ordinarily, infants are apt to take anything into the mouths and do not have a sufficient discriminating capability. Therefore, troubles of infants due to swallowing by mistake and biting by mistake occur at a high trouble occurrence rate.
In view of the above circumstances, as for the markedly small magnetic disk cartridges described above, it is necessary to take safety countermeasures for preventing the troubles of infants due to swallowing by mistake and biting by mistake from occurring. Particularly, even though it may not occur that the magnetic disk cartridge is swallowed by mistake, if the magnetic disk cartridge is taken into the mouth or is licked, the saliva, and the like, will adhere to the recording surface of the magnetic disk cartridge, and an error in recording and reproduction of information will occur.